Field of the Invention
The present invention relates to a system for pelletizing Solid Refuse Fuel (SRF) to recycle plastic waste that occurs after plastic is used for agricultural, domestic, and industrial purposes. The present invention more particularly relates to a system for pelletizing SRF to recycle plastic waste instead of incinerating or disposing of plastic waste in landfills, without using cleaning water for cleaning the plastic waste, thereby preventing environmental pollution, more specifically water pollution.
Description of the Related Art
Generally, vinyl or plastic waste that occurs in a large amount in agricultural and fishing villages and industrial sites does not naturally degrade. Accordingly, it has so far been usually incinerated or disposed of in landfills. In the case of incineration, toxic fumes and incinerator ash containing hazardous heavy metals are generated, causing air pollution. On the other hand, in the case of disposal in landfills, it takes a very long time for the plastic waste to degrade or decay, also causing soil contamination. Therefore, reuse of plastic waste is a good way of dealing with plastic waste.
The most common practice to recycle vinyl or plastic waste is as follows (also, refer to the process flow of FIG. 1): collected vinyl or plastic waste is crushed or shredded by a crusher 1; the crushed or shredded raw material and water are put into a washing tank 2, so that impurities adhered to the crushed or shredded raw material are removed from the raw material; the raw material free of impurities is dehydrated in a dehydration tank 3; the dehydrated raw material is put into a melt-extruder 4 so as to be fused by heat, and then discharged outside the melt-extruder 4; the fused raw material is extruded through a predetermined size of a hole and cut into extrusion-molded beads having a predetermined size by a cutting device 5; extrusion-molded beads that are extruded and cut are thrown into a cooling tank 6 so that the extrusion-molded beads would not stick to each other; and the extrusion-molded beads are cooled down to a water temperature in the cooling tank 6, becoming pellets 7.
This recycling method uses a wet cleaning process in which water is used. Accordingly, although it is possible to almost perfectly remove impurities from the plastic waste, it is difficult to completely remove water from the plastic waste through the dehydration process. For this reason, the pellets are likely to contain moisture, resulting in degradation in quality of recycled products. Meanwhile, a hot air drying process may follow the dehydration process for perfect removal of moisture that remains after cleaning. However, this process increases recycling cost, resulting in a decline in competitiveness of the recycled products.
Korean Patent Application Publication No. 10-2007-0102789 (Patent Document 1) proposes a solution to this problem.
The device proposed in Patent Document 1 includes: a driving unit; a conveyer screw including a first bar-like body that is rotated by the driving unit, and helical threads that are formed at regular pitches on an outer surface of the first bar-like body and wound in a direction in which the bar-like body rotates; a dehydration screw including a second bar-like body that is rotated by the driving unit and shorter than the first bar-like body of the conveyer screw, and helical threads that are formed at regular pitches on an outer surface of the second bar-like body, wound in the same rotation direction of the first bar-like body, and arranged to be misaligned with the helical threads of the conveyer screw; a filter housing that has an inlet in a front portion and an outlet in a rear portion, encases the conveyer screw and the dehydration screw therein, has an internal diameter corresponding to an external diameter of the helical threads, and has a water discharge hole formed in a portion where the dehydration screw is arranged; and a heating unit that fuses plastic waste transported by the conveyer screw. The device can achieve a dehydration effect using the conveyer screw and the dehydration screw while fusing the plastic waste.
However, since the device uses a cleaning process using water, a dehydration effect cannot be sufficiently obtained.
The foregoing is intended merely to aid in the understanding of the background of the present invention, and is not intended to mean that the present invention falls within the purview of the related art that is already known to those skilled in the art.
Documents of Related Art
(Patent Document 1) Korean Patent Application Publication No. 10-2007-0102789 titled “Melting Extruder for Recycling of Plastic Waste and Pelletizing System for Plastic Waste Using the Same” (published on Oct. 22, 2007)